Analysis and Effects of Process Parameters in Induction Hardening

27 January 2017

Induction hardening technology employs a refined control setup, with magnetically induced energy patterns acting as a contact-free heat treatment mechanism. A hardening profile is established by the induction station’s electrically manipulated magnetic fields. Science-based principles now gain traction, but what criteria are we hinting at here? A detailed analysis is required to understand the effects of these process parameters.

Process Parameters: A Brief Primer 

Electromagnetic fields hold sway during the hardening cycle. The outer section of the processing station is surrounded by a series of coils, windings that selectively generate induction currents. The workpiece responds to the eddy currents on a molecular level by inducing great quantities of thermal energy. Logically, the process is finitely controllable. All that’s require is mastery of the electrically regulated coils.


The cycles-per-second generated by the power supply inversely affect hardening depth. That is, lower frequencies produce thick case hardened surface layers. Conversely, thinner hardened layers are spawned when higher frequencies are applied. An analysis of this process parameter indicates a need for a supremely uniform power supply. Otherwise, frequency inconsistencies could undermine the phase transformation process.
Inside The Process


The Joule heating mechanism (the coil) is a physical construct, but its operation is ruled by frequency responses, hysteresis losses, and power density considerations. When power is applied, the austenitizing temperature is reached and the surface of the workpiece transforms. The generated fields selectively target gear teeth and other complex geometrical outlines while larger magnetic currents envelop whole pieces. The contact-less process only concludes when the flux density enveloping the workpiece has transformed the material all the way down to a predetermined depth.
Analyzing Process Parameters


Uniform surface coverage is maintained by the power supply and the induced field. Frequency and voltage settings strengthen or weaken the field and dictate hardening depth. Naturally, the thickness of the component and its geometry will also impact the process, but these factors are typically accounted for by the heat treatment engineering team. There are undermining influences at work, though. For example, electromagnetic end effects will hamper part’s treatment. The end effect distorts the induction field pattern at the coil end regions. These and other field distorting effects require careful monitoring.

Fortunately, the electromagnetic fields are monitored in real-time, which is why the selected conditioning of gear teeth and the uniform treatment of large-scale workpieces both benefit from this potent heat treatment method. The only absolute necessity, a requirement that will assure predictable process parameters, is a non-fluctuating power supply, an induction source that’s designed to be implemented in induction hardening applications.

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